P R E S E N T E D B Y
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
SAND2019-XXXX C
Atmospheric Transport Results for BSAF Phase 2
N. E. Bixler
Coauthor: D. J. Clayton
Sandia National Laboratories
P re s e nte d at 1 1
t hE M U G M e et i n g , April 4 – 5 , 2 0 1 9 , Brug g ‐ Windisch, Swit ze r land
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Contents
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Objectives
Sources of uncertainty
Results
Summary
Objectives of Atmospheric Transport Analysis at Fukushima
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Provide guidance to source‐term modelers by estimating ground deposition patterns
Focus on Cs‐137 (best quantified of the released isotopes)
Deposition pattern depends critically on chronological alignment of release with weather pattern
Benchmark atmospheric transport models against real data
HYSPLIT Lagrangian particle tracking model
As a stand‐alone model
Integrated with MACCS
Two Major Sources of Uncertainty
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Uncertainty in weather was investigated using three sources of weather data, all from NOAA
WRF (Weather Research and Forecasting) model, generated in 2014
4‐km spatial, 20 min temporal discretization
No nudging
GDAS (Global Data Assimilation System)
0.5 degrees spatial, 3 hour temporal discretization
No nudging
WRF model, generated in 2017
4‐km spatial, 5 min temporal discretization
Nudged with observations
Uncertainty in source term was assessed using source
terms from BSAF contributors
Meteorological Data for First 7 Days
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Weather data have similar trends
but
Significant variations in
detail
Evolution of Integral Release Estimated by NRC/SNL
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Curves indicate evolution of integral release for three units as estimated by NRC/SNL over the course of BSAF Phase II
Many of the initial and boundary conditions needed to estimate accident progression were poorly understood
Initial damage state was unknown
Water injection may have failed, succeeded, or partially succeeded
0 5 10 15 20 25 30 35 40
0 5 10 15 20 25 30
Cs-137 Integr al Release (PBq)
Elaspsed Time (day)
H Terada et al.
IRSN
IRSN (update) JAEA/NSC JNES/TEPCO Stohl et al.
TEPCO Winiarek et al.
ZAMG
SNL MELCOR 7/2016 SNL MELCOR 1/2017 SNL MELCOR 7/2017 SNL MELCOR 1/2018 SNL MELCOR 5/2018
Weather Data Comparison
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Plots use
• Consistent scale
• Consistent
isopleth shading (1 additional level in SNL plots)
SNL MELCOR 5/2018 WRF 2017
WRF 2014 GDAS
Predicted Ground Deposition
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WRF 2017 SNL MELCOR 5/2018 Source Term
Contributions to Deposition Pattern from Individual Units
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• Figures show final deposition patterns created by each unit based on final NRC/SNL source term using WRF 2017 weather data
• Unit 1 contributes very little to the overall pattern
• Unit 2 and, to a lesser extent, Unit 3 create much of the NW deposition pattern, mostly on 3/15
Unit 1 Unit 2 Unit 3
BSAF Source Terms
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SNL received source terms from eight BSAF organizations
Four provided a source term for all three units
GRS (Germany) reconstructed a source term using data from radiation monitors in the area surrounding Fukushima
(reverse method)
Organization Country Code Units SNL USA MELCOR 1, 2, & 3
IAE Japan SAMPSON 1, 2, & 3 IRSN France ASTEC 1, 2, & 3 KAERI Korea MELCOR 1, 2, & 3
CIEMAT Spain MELCOR 1
CNL Canada MELCOR 2
CRIEPI Japan MAAP 2
PSI Switzerland MELCOR 3
Total Source Term Comparison
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Total Deposition Comparison
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GRS REVERSE METHOD NRC/SNL MELCOR
IRSN ASTEC
IAE SAMPSON KAERI MELCOR
Using WRF 2017 Weather Data
Summary of Fukushima ATD Modeling
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NRC/SNL evaluated atmospheric transport with HYSPLIT and MACCS
Uncertainty in meteorology makes a significant difference in the deposition pattern
Uncertainty in source term makes an even larger difference in the deposition pattern
Insights from atmospheric transport modeling
improved the fidelity of the source terms over the course of BSAF Phase II
BSAF results have provided preliminary guidance
for decommissioning the Fukushima Daiichi units
List of Acronyms
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ATD Atmospheric Transport and Dispersion
BSAF Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station Project CRAC Calculation of Reactor Accident Consequences
DCF Dose Conversion Factor
DHS Department of Homeland Security GDAS Global Data Assimilation System
GDP Gross Domestic Product
HYSPLIT Hybrid Single Particle Lagrangian Integrated Trajectory MACCS MELCOR Accident Consequence Code System
MUPSA Multi‐Unit Probabilistic Safety Assessment
NISAC National Infrastructure Simulation and Analysis Center NOAA National Oceanic and Atmospheric Administration NRC Nuclear Regulatory Commission
PRA Probabilistic Risk Assessment
RDEIM Regional Disruption Economic Impact Model REAcct Regional Economic Accounting tool
SGTR Steam Generator Tube Rupture SNL Sandia National Laboratories
SOARCA State‐of‐the‐Art Reactor Consequence Analyses WRF Weather Research and Forecasting Model